The major long range objectives of the proposed research are to determine the mechanisms which regulate RNA synthesis and RNA polymerases during developmental transitions. Emphasis is placed on transitions where highly quiescent tissue is induced to proliferate. Specific objectives include: 1) To determine what subunits are common to RNA polymerases I, II, and III and to determine whether any subunits that have different molecular weights or charge densities in the enzymes are immunologically related. This will be investigated by separating the RNA polymerases into subunits, covalently coupling the subunits to diazobenzyloxymethyl (DEM)-paper, and analyzing for common antigenic determinants by reacting the paper with specific antibodies to RNA polymerases I, II, and III and detecting subunit-antibody complexes with 125I-labeled protein A from Staphylococcus aureus. 2) To determine whether RNA polymerase IIA or IIB is the enzyme active in in vivo transcription of mRNA genes. This will be investigated by immunoprecipitating RNA polymerase II from crude extracts which have been homogenized in the presence of protease inhibitors or denaturing agents which prevent proteolysis. Protease activities in chromatin and other cellular fractions will be detected by utilizing 3H-labeled RNA polymerase IIA as substrate. RNA polymerases IIA and IIB will be tested on defined templates for efficiency and selectivity of transcription. 3) The activation of RNA polymerase I in rapidly proliferating tissues will be investigated. This will involve the use of recombinant DNA since rDNA sequences will be cloned in lambda or bacterial plasmids to facilitate in vitro transcription studies designed to define parameters required for faithful transcription by RNA polymerase I and to determine what components regulate transcription of ribosomal RNA genes.